1. Technical Field
The embodiments herein generally relate to mobile television (TV) technologies, and, more particularly, to techniques for viewing and selecting mobile TV programs.
2. Description of the Related Art
Handheld devices with integrated digital television access are a relatively new phenomenon. Such technology has traditionally been limited by size, power consumption, and most importantly performance. Poor performance of such devices has typically been the result of the constantly changing receiver environment. More particularly, the quality of the received signal is affected by the device's ability to manage adjacent-channel rejection, low signal-to-noise ratios, and Doppler compensation, among other factors.
Digital Video Broadcasting—Handheld (DVB-H) is the specification for bringing broadcast services to handheld receivers, and was formally adopted as an ETSI (European Telecommunications Standards Institute) standard in November 2004. More specifically, DVB-H is a terrestrial digital TV standard that tends to consume less power than its predecessor, the DVB-T standard, and generally allows the receiver to move freely while receiving the signal transmission, thereby making it ideal for cellular phones and other mobile devices to receive digital TV broadcasting over the digiTV network, and hence without having to use cellular telephone networks.
In mobile TV DVB-H systems such as DVB-H (ETSI EN 301 192), one radio frequency (RF) channel is shared among many TV channels (TV programs). These TV channels are multiplexed either in the time domain or in the frequency domain. When the TV channels are multiplexed in the time domain, each channel is given full access to the whole RF channel bandwidth for a short period of time (burst duration). After that burst is transmitted, bursts for other channels occupy the RF channel and so on. This multiplexing process is called time division multiplexing (TDM). FIG. 1 shows an example of time division multiplexing of 15 TV channels on one RF channel. The TV channels are labeled 1, 2, 3, . . . , 15. In FIG. 1, it is shown that each TV channel occupies the whole RF channel for 1/15 of the time. A receiver which is watching only one channel (for example, CH2) needs only to be active (ON) during the periods of CH2 bursts. In order to conserve battery consumption, such a receiver will shut off its circuits when CH2 bursts are not occupying the RF channel. It thus becomes in a SLEEP mode. This shows that TDM of channels can help reduce power consumption of a receiver watching a single channel.
On the other hand, this causes a problem when the user wants to switch to watch another TV program on the same RF channel. One example is shown in FIG. 1, if the user wishes to switch to CH3 (denoted by Channel UP in FIG. 1). The worst case occurs when the user issues a command to switch to CH3 right after the burst of CH3 ends. In this case, the receiver has to wait until the next burst that belongs to CH3 appears on the RF channel. This causes the user to wait for a given period of time denoted as the channel switching delay. Such a delay could be as long as 5 to 7 seconds in DVB-H systems. Such a channel switching delay could be rather annoying to the user, especially when the user is flipping through channels trying to check the content in all of the channels.
One way around this would be to create a visual program guide, which can display the content of multiple channels simultaneously. The user browses the content of all of the channels without the need to flip through all channels by switching from one channel to the other (i.e., by manually switching from one channel to the other). The user then decides on which channel to switch to. However, one of the problems with this approach is that the video decoder will be required to receive and decode many programs simultaneously. This adds significant complexity and power consumption to the video decoder being used. Furthermore, it requires the use of a very fast interface between the demodulator and video decoder which could be very costly in terms of power consumption.
Another scenario is that the demodulator senses that the user wishes to flip through the channels. The demodulator then decodes all channels and buffers a single burst of each channel. The demodulator forwards the requested channel burst when the user switches to this channel. However, one of the problems with this approach is that the demodulator has to store a significant amount of video which requires the use of a lot of memory. Accordingly, there remains a need for a technique capable of allowing a viewer to select mobile TV channels in a more user-friendly manner and which reduces batter power consumption.